Asystole and pulseless electrical activity (PEA) are cardiac rhythms with a very poor prognosis. When a patient suffers from asystole, the heart of the patient fails to contract. No ventricular depolarization takes place in the heart, cardiac output stops, and the patient is near death. The failure of the heart to generate a ventricular depolarization may be due to a failure of the electrical system of the heart, or may be caused by factors other than the electrical system.
PEA is the term applied to a group of conditions in which there may be detectable cardiac electrical activity but no detectable pulse. Although electrical activity is present in PEA, cardiac contractions may be absent. As a result, the heart of a patient suffering from PEA may produce insufficient cardiac output.
Asystole and PEA are grave cardiac rhythms. A patient experiencing either rhythm will die unless the heart assumes a contractile rhythm that restarts circulation. Unfortunately, asystole and PEA are typically not responsive to a defibrillation shock. Even if treated with medication and cardiopulmonary resuscitation (CPR), the odds of survival for the patient are low.